What you’re seeing
- Outside senders get '550 5.4.1 Recipient address rejected: Access denied' when emailing a valid employee.
- The rejected address exists and the person can send mail and receive internal messages normally.
- The bounce often includes a reference to Directory-Based Edge Blocking.
- Only addresses in one domain or one newly added alias are affected.
Common causes
Every environment is different, but these are the causes our engineers find most often:
- The address being used is not attached to any mailbox, group or contact in Microsoft 365, so it is rejected at the door.
- Directory synchronization from on-premises Active Directory has not yet copied the new address to the cloud.
- The domain is set as authoritative in Microsoft 365, but some of its users still live on another mail system.
- A new domain was added but MX records point to Microsoft 365 before all recipients were set up there.
- A recently deleted or renamed mailbox left the old address with nothing behind it.
Why it matters
Customers trying to reach a real employee are told the address doesn't accept their mail, which looks to them like the person has left or the business has closed. Applications, orders and support requests are lost, and the sender rarely tries another route. During migrations or after a new domain is added, this can affect a whole group of staff at once and go unnoticed until someone asks why replies stopped coming.
How AskTechGurus fixes it
Skip the trial and error. A certified engineer works on your actual system, finds the root cause, and fixes it properly.
Tell us what’s happening
Submit a ticket in about two minutes. Paste the error, describe what changed, and pick your tier. No charge to submit.
A certified engineer diagnoses it
A vetted, US-based systems engineer claims your ticket, usually within minutes during business hours, and investigates over a secure remote session you can watch and end at any time.
Fixed and verified with you
The engineer resolves the root cause and confirms with you that it’s working. You don’t just get a workaround, and you get a plain-English summary of what was wrong.
Pay only when it’s resolved
Fixed price from $99, invoiced only after you approve the fix. If it isn’t resolved, you don’t pay.
Frequently asked questions
Why would Microsoft reject mail for someone who works here?
Microsoft 365 checks every incoming address against your directory before accepting it. If the exact address isn't listed there, even for a real person, it is refused to cut down on spam.
Will the senders have to resend their messages?
Yes. Rejected messages are returned to the sender and are not held anywhere, so important contacts may need to be asked to send again.